The Destiny of the Body

Chapter IX

The Evolutionary Clues

Conceivably, one might rediscover and re-establish at the summit of evolution of life the phenomenon we see at its base, the power to draw from all around it the means of sustenance and self-renewal.

(Sri Aurobindo, The Supramental Manifestation upon Earth, p. 52)

It is evident that spontaneous motion or locomotion, breathing, eating are only processes of life and not life itself; they are means for the generation or release of that constantly stimulating energy which is our vitality and for that process of disintegration and renewal by which it supports our substantial existence; but these processes of our vitality can be maintained in other ways than by our respiration and our means of sustenance.

(Sri Aurobindo, The Life Divine, pp. 177-78)

Evolution, being...continuous, must have at any given moment a past with its fundamental results still in evidence, a present in which the results it is labouring over are in process of becoming, a future in which still unevolved powers and forms of being must appear till there is the full and perfect manifestation.

(Ibid., p. 707)

In spite of their wide diversity, all living things, we have seen, have three major nutritional requirements: energy-yielding organic compounds, structure-producing organic compounds and a few mineral trace elements. In particular, carbohydrates, proteins and fats are the three categories of organic foodstuffs demanded by all higher living forms, along with oxygen as the energy-releasing agent.

But are all these things absolutely essential for the maintenance of life-process ? Also, cannot a living body manage to synthesize in situ all its nutritional requirements out of materials gathered solely from the inanimate inorganic realm?

Page 283

In an attempt to seek for possible answers to this double question, when we scan the whole gamut of living physical existences we find here and there important clues which show unmistakably that Nature has experimented in exceptional circumstances with all sorts of possibilities. The results achieved, although partial, have from our point of view far-reaching significance. Let us mention en passant only a few of these glimmering signposts.

Phenomena of interconversion: Experimental investigations have demonstrated the fact that in case of exigency a living body can transform in however small a measure any of the three classes, carbohydrates, proteins and fats, into any other form.

Thus proteins can cause formation of carbohydrates under certain special conditions. "In a diabetic animal or in an animal poisoned with the drug phlorizin, there is a great loss of sugar from the body.... In such an animal, the carbohydrate stores are rapidly depleted. If now carbohydrates be withheld from the diet but protein be given it is found that the excretion of glucose continues, and this must have been derived from protein."¹

Carbohydrates on their part can be converted into body fat. This was well demonstrated by the classical experiments of Lawes and Gilbert. "Young pigs were fed on a diet of barley containing very little fat, and it was found that the amount of body fat present when the animals were killed was greater than could have been obtained from the fat supplied or even the fat and protein together, thus proving that carbohydrates can be converted into fat."²

That fats in their turn can undergo metabolic transformation into carbohydrates or even into proteins has been definitely shown by means of ingested fats previously labelled with radioactive carbon. Indeed, so far as carbohydrates are concerned, these can be produced in the body, in the forms of glycogen and glucose, out of protein and carbohydrate foods. "The process of formation of glucose from non-carbohydrate sources, which is conveniently described by the word 'gluconeogenesis', is responsible for the maintenance of the blood sugar concentration when carbohydrate is not being ingested at a rate sufficient to supply the needs of the body; that is during post-absorptive conditions, starvation, and when the animal receives a low-carbohydrate diet."³

^{1 2} F. R. Winton & L. E. Bayliss, Human Physiology (1955), p. 200.

³ Ibid., p. 206.

Page 284

Needs secondary and incidental: We have seen in Chapter VII that almost all chemical reactions in the body are mediated by enzymes and the effectivity of these biocatalysts is in many cases absolutely dependent on their co-enzymes or prosthetic groups. Now these co-enzymes may consist entirely or in part of metallic elements such as Iron, Copper, Manganese, Zinc, Vanadium or Molybdenum. On the other hand, elements like Potassium, Boron or Chlorine activate several important enzymes. Thus, from the nutritional point of view, these trace elements that function as components of enzyme systems are not the primary or absolute needs of the body; their necessity arises because of the special metabolic machinery provisionally put into operation by Nature and these intermediaries can be very well discarded if another physiological base is devised for the body.

The non-essentiality of oxygen: A few creatures like the parasites in the intestine where the availability of oxygen is almost nil, can live without this vital oxidising agent by tapping "the energy from chemical processes, such as the formation of lactic acid from glucose, which do not require oxygen."¹ This type of metabolism has been termed anaerobic (from GK. an, not; aer, air; bios, life) and, as we shall presently see, the photosynthetic formation of carbohydrates by green plants from carbon dioxide gas is such an anaerobic process.

Also, since it has been demonstrated that the terrestrial atmosphere at the time of the appearance of the first organism upon earth was reducive in nature, containing no oxygen, the first forms of life must have found some means of circumventing the need for this element.

Organic synthesis from inorganic raw materials: We have seen that carbohydrates, proteins and fat are somewhat mutually convertible so that all of them may not be absolutely needed at the same time. But they are all organic foodstuffs; so the very first category that may theoretically give rise to the formation of the other two has perforce to be organic and thus must have its source in the bodies of other organisms. Because of this necessity for preformed complex organic compounds as their food, all complex forms of life including humans are absolutely dependent

¹ Knut Schmidt-Nielsen, Animal Physiology (1963), p. 13.

Page 285

upon other living bodies for satisfying their nutritional requirements.

But the fetters of this dependence are loosened in the case of some lower forms of life. Thus some micro-organisms require for their viability "no complex organic material whatsoever. Nitrogen (usually as an ammonium salt), carbon (as a simple salt such as carbonate) and minerals are sufficient to provide optimum growth and reproduction in such organisms."¹ Some of these organisms such as purple and green bacteria meet their energy-needs by fixating the energy of sunlight by means of special bacterial pigments: for this reason, they have been termed photo-synthetic organisms. Some other micro-organisms (e.g., chemosynthetic bacteria), instead of drawing upon solar energy, obtain their energy "by harnessing the chemical energy of some inorganic process such as the oxidation of ammonia to nitrite or nitrate, the oxidation of hydrogen sulphide to elemental sulphur, or that of ferrous compounds to the ferric state."²

Apart from these self-supporting micro-organisms, all green plants are extremely modest in their nutritional needs. As is well known, these plants can produce by photosynthesis an astonishing variety of organic compounds including proteins, vitamins and hormones — in fact all the complex organic stuff that they require for their life-processes — from a handful of simple inorganic materials such as water, carbon dioxide, a few mineral salts and ammonia or nitrate.

The mystery of nitrogen fixation: Green plants are indeed so versatile in the matter of organic synthesis! But even they fail to utilise the nitrogen present in such huge abundance in the earth's atmosphere and have to depend for this essential element upon ammonia or nitrate. And this is so because nitrogen is present in air in the form of very stable nitrogen molecules. These molecules must somehow be destabilized and cleaved before nitrogen can be made available for utilization by life.

But Nature has experimented with this process too and the fixation of atmospheric nitrogen by a living organism — "one of the most important, yet one of the least understood, reactions in

¹Article entitled "Nutrition" in Encyclopaedia Britannica (1966), Vol. 16, p. 650.

²Ernest Baldwin, Dynamic Aspects of Biochemistry, p. 230.

Page 286

all biochemistry"¹ — has been a realised fact. "This complex of reactions is achieved by certain bacteria that live on the organic matter in the soil...and also by certain associations of bacteria living in swellings, or nodules, of particular plant roots.... In addition, certain blue-green algae (such as Nostoc) and photosynthetic bacteria (such as Rhodospirillum) are capable of fixing atmospheric nitrogen."²

Variability of needs for organic compounds: We have found that most organisms absolutely require in their dietary regimen the provision of some 'growth factors'. These have been defined as organic compounds which are essential for the maintenance of a particular organism but which the organism cannot synthesize within its body from other available materials. Amino acids, constituents of protein molecules, and various vitamins are typical growth factors for many living bodies and hence must be provided from outside.

But what is of great significance from our point of view is the discovery that the dietary needs for these growth factors vary widely from species to species and, in some special conditions, even from member to member of a single species. And this divergence arises from the fact that different organisms differ enormously in their ability to synthesize organic compounds. Most organisms are capable of making many of the growth factors themselves, but not all of them. Thus what is an absolute dietary essential for one species may be without effect in another since the latter may be capable of synthesizing it from other materials.

Thus the nutritional requirements for the essential amino acids can vary from zero, in the case of plants and some micro-organisms that synthesize them all, to the complete list of 20-25 known amino acids in the case of an organism that has lost all power of synthesis. Man's body cannot synthesize eight or ten of these amino acids; so these must be provided in a human diet.

The same sort of variability one finds in vitamin requirements of different species, the need for a particular vitamin indicating a synthetic disability of the organism.

The foregoing study reveals that, in the last analysis, it is solely a question of synthetic ability or disability which will determine

^{1 2} A. W. Galston, The Life of the Green Plant (1963), p. 44.

Page 287

whether a particular type of organism can be independent of any external supply of organic foodstuffs. And this brings us to the characterization of what have been termed autotrophic and heterotrophic organisms.

The autotrophes¹, the heterotrophes and food chains: On the basis of the synthetic ability manifested in various degrees by different organisms, living bodies have been broadly divided into two groups: autotrophes and heterotrophes.

The autotrophes are those organisms that, like green plants and chemo- and photo-synthetic bacteria, are "competent to synthesize all the structural, catalytic and storage materials they need for growth, maintenance and reproduction: everything their life requires can be produced from the simplest of starting materials, the necessary energy being collected from the external world."² Since in the case of these autotrophes, 'food' has not to be brought in from outside the organism but can be produced in situ in its own body, out of inorganic materials alone, these organisms are absolutely independent of other organisms for their nutritional requirements.

The heterotrophic organisms stand in sharp contrast to the autotrophes. For "not even the most versatile of heterotrophic forms can live except by exploiting the industry and synthetic ingenuity of other organisms. Only by fermenting, oxidizing, or in some other way degrading complex organic material, can the heterotrophes obtain the energy required to maintain themselves."³ Heterotrophic organisms are incapable of synthesizing their basic constituents such as amino acids, vitamins, carbohydrates and so forth, and are thus dependent upon other organisms for a supply of these essential organic 'foods'.

Generally speaking, all plants excepting those few lacking chlorophyll, such as mushrooms, are autotrophic in nutrition. They fixate the energy of sunlight to produce all that they themselves need and all that animals need; for, all other organisms being heterotrophic have to secure their food directly or indirectly from the autotrophic vegetable kingdom.

It is because of this difference in bio-synthetic capabilities that Nature has had to devise the process of mutual devouring and set

¹ 'Autotrophs' = self-nourishing; 'heterotrophe' = gathering food from other sources; from Gk. autos, self; heteros, others; trophe, food. ^{2 3} Ernest Baldwin, op. cit., pp. 230-31.

Page 288

up what has been called 'food chains'. "A food chain typically begins with green plants, which are exploited by herbivorous animals and these, in their turn, by carnivores. These become the prey of larger and more powerful carnivores and so on....Always in these food chains the starting-point is with autotrophic organisms. Herbivorous animals rely at first hand, and carnivores at second or third hand, upon the autotrophes for supplies of their numerous essential substances which they require, as well as for a sufficiency of complex energy-yielding organic foodstuffs. Gathered together in the first instance by herbivorous beasts these essential materials are passed stage by stage along the food chains."¹

We see then that bio-synthetic disability is not an attribute universal to all life nor is it the same, qualitatively or quantitatively, in all those organisms that manifest it. These findings of modern biological sciences are indeed of great import; for they show that the central objective envisaged in our essay, — how to make a human body autotrophic in nutrition ? — is not, even from the point of view of present-day science, altogether chimerical and impossible of accomplishment.

Step-wise loss of synthetic ability: Indeed, experimental work conducted by Beadle, Tatum and others on mutant strains of some micro-organisms has demonstrated beyond any doubt that, in the course of evolution, the original versatile bio-synthetic capability has been supplanted by its progressive loss incurred in a step-by-step process.

As a matter of fact, modern researches have shown that the actual metabolic pathways by which various living bodies synthesize or degrade biologically important particular organic compounds like the vital amino acids are the same in all cases. "Bio-synthetic mechanisms thus appear to have developed soon after the origin of life, and to have remained unchanged throughout the divergent evolution of modern organisms."²

Now the different links in a particular pathway of biochemical reactions are mediated by different enzyme systems and if for one reason or another a particular link is snapped or the pathway blocked in the living system of an organism, this organism will be incapable of synthesizing the whole series of later products and require them to be supplied artificially in its diet. This is what has

¹ Ernest Baldwin, op. cit., p. 233.

² McGraw-Hill Encyclopaedia of Science and Technology, Vol. I, p. 314.

Page 289

happened in the course of evolutionary elaboration of the organic realm.

The original organisms could synthesize all their needs metabolically and none were required nutritionally. But "as evolution progressed, food chains developed, and some forms of life became adapted to obtain many of their organic nutrients at the expense of other living forms, either directly or indirectly. In the dependent types, mutations had occurred causing the loss of specific biosynthetic enzymes and hence the gain of [nutritional] requirements."¹

Thus the loss of biosynthetic capability is only fortuitous and incidental and not at all intrinsic to the very life-process. And this fact opens wide the gates to future evolutionary possibilities, and the ultimate conquest of the body's food-needs becomes a feasible proposition. Let us see how.

¹ McGraw-Hill Encyclopaedia of Science and Technology, Vol. I, p. 314.

Page 290